It’s possible to get a better deal here than at the shops run by NPCs

Transportation: Many methods of transportation are available to help adventurers travel between the nations of Vana'diel. Some have made appearances in previous FINAL FANTASY titles, like Rumble Fighter gold airships, chocobos, and ferries.

Trade: The Trade system lets players securely transfer money and goods between themselves, and also give items to NPCs for the myriad quests in the game.

The Auction: In the auction houses of FINAL FANTASY XI, sellers designate an asking price when they put items up for bid. The first bidder to offer a price higher than the asking price gets to purchase the item. These places are a magnet for players, since it's possible to get a better deal here than at the shops run by NPCs.

Bazaar: Players can also hawk items themselves with the Bazaar system. Just set a price on any item in your inventory -- any players targeting you can easily check for items you have for sale and buy them immediately.

Crystal Synthesis: Through crystal synthesis, players can create a fantastic variety of items, many of which are unavailable in shops. The system is flexible and lets players experiment to make the items they want.